MICROCERATOPS(pronounced MY-cro-SER-ah-tops) Microceratops (meaning "small horned face") was a very small, frilled, plant-eating dinosaur only 30 inches long (76 cm). Its upper front leg bone was only 4 inches (10 cm) long. It was very similar to Protoceratops but smaller, with thinner limbs, and it may have been able to run on two legs. It lived during the late-Cretaceous period, about 83 to 65 million years ago in what is now China. It was named by Bohlin in 1953.

MICROCOELUS(pronounced MY-croh-SEEL-us) Microcoelus (meaning "tiny hollow (vertebra)") was a titanosaurid sauropod, a plant-eating saurischian dinosaur. It lived during the late Cretaceous period. Microcoelus walked on four sturdy legs, had a long neck, long tail, thick bones, a bulky body, five-toed feet, and a small head. Fossils have been found in Argentina, South America. Microcoelus was named by paleontologist Lydekker in 1893. Microcoelus is a dubious genus and may be the same as Saltasaurus.

MICRODONTOSAURUS(pronounced MY-croh-DONT-oh-SAWR-us) Microcrodontosaurus (meaning "tiny tooth lizard") was a sauropodomorph, a plant-eating dinosaur. It lived during the late Cretaceous period. Microcrodontosaurus had a long neck, long tail, a bulky body, and a small head. The hind legs were much larger than the front legs. Fossils have been found in China. The type species is M. dayensis; it was named by paleontologist Zhao in 1985 [it is a nomen nudum].

MICROPACHYCEPHALOSAURUS(pronounced MY-cro-PACK-ee-SEF-ah-lo-SAWR-us) Micropachycephalosaurus (meaning "tiny thick-headed lizard") was a very small pachycephalosaurid, a thick-skulled, plant-eating ornithischian dinosaur. It was about 1.5-3 feet (0.5-1 m) long and weighed roughly 22-33 pounds (10-15 kg). It lived during the late Cretaceous period, about 83 to 73 million years ago. Its fossils have been found in China; only a very incomplete specimen has been found. Micropachycephalosaurus was named in 1978 by the Chinese paleontologist Dong. The type species is M. hongtuyanensis. Micropachycephalosaurus has the longest name of any dinosaur.

MICRORAPTOR(pronounced MY-cro-RAP-tor) Microraptor (meaning "little plunderer") is a newly-discovered, bird-like dinosaur from China. This crow-sized coelurosaurid theropod was about 16 inches (40 cm long). Its feet were adapted for climbing; it have spent much of its life in trees. This bipedal meat-eater had some bird-like features, including its teeth (like those of early birds) and hip (it had a Rahonavis-like ischium). A partial skeleton (missing the middle portion) and feather-like impressions were found in Liaoning, China. It is probably an adult, but this is not certain. The type species is M. zhaoianus; it was named by Xu, Zhou, and Wang in 2000.

MICROVENATOR(pronounced MY-cro-vee-NAY-tor) Microvenator (meaning "small hunter") was a small, fast-moving, long-legged, meat-eating, bipedal dinosaur about 4 ft. (1.2 m) long, weighing perhaps 6.5-14 pounds (3-6.4 kg). This turkey-sized predator was an advanced theropodthat lived during the early Cretaceous period, about 119 million to 113 million years ago, in what is now Montana, USA. It was named by paleontologist John H. Ostrom in 1970. It is known from a partial skeleton. The type species is M. celer.

MIGRATIONMigration is a yearly movement in which some animals travel to avoid bad weather, to find food, or to reproduce. Some migrators (animals who migrate) travel short distances, other go thousands of miles. Migrators travel by flying, swimming, walking, hopping, burrowing, or slithering. True migrators make a two-way trip each year from one place to another and back again.Most migrators travel north and south, but some, like the umbrellabird and the earthworm, migrate vertically (up and down). Some dinosaurs may have migrated; Edmontosaurus, for example, may have migrated..

MILANKOVITCH THEORYThe Milankovitch Theory attempts to explain major temperatures changes on Earth, especially ice ages, by slight variations in the amount of sunlight reaching the Earth caused by the eccentricity of the Earth's orbit around the Sun. The Earth's orbital eccentricity changes the Earth's average distance from the sun and therefore slightly changes the amount of sunlight reaching the Earth. Milankovitch looked over the past 600,000 years and correlated summer temperature mimnima with four major ice ages in this time. Eccentricity cycles last over 100,000 years. This theory was proposed by Milutin Milankovitch in 1938. Recently, scientists (Richard A. Muller and Gordon J. MacDonald, July 11, 1997, Science) have found that changes in the axal tilt of the Earth's orbit more closely match glacial cycles for the past million years.

MILES, CLIFFORDClifford Miles ia a paleontologistwho, together with his associates, re-opened the fossil collection from the Bone Cabin Quarry of the American Museum of Natural History. In this fossil cache, they found the first skull and skeleton of a Jurassic ankylosaur, Gargoyleosaurus, which Miles helped describe. He also found a nearly-complete adult Camarasaurus grandis (now exhibited at the Gunma Museum of Natural History in Japan). This skeleton was described in a monograph written by Cliff and his colleagues (including Jack McIntosh).

MILLIONA million is a thousand thousand. The dinosaurs lived millions of years ago.

MINERALA mineral is a naturally-occurring solid of definite chemical composition whose atoms usually form a regular pattern.

MINMI(pronounced MIN-mee) Minmi was an unusual Australian ankylosaur 10 feet (3 m) long from the early Cretaceous period. Minmi was named by Molnar in 1980, for the Minmi Crossing, north of Roma in southeastern Queensland, Australia.

MIOCENE EPOCHThe Miocene epoch was a geologic time span that lasted from 24 million to 5 million years ago. During the Miocene, modern birds and many mammals evolved (including the horses, dogs, bears, South American monkeys, and apes in southern Europe). Ramapithecus appeared; this primate was pehaps an ancestor of man. The climate was relatively warm (as compared to the earlier Oligocene or the later Pliocene). There were extensive grasslands (and grasses diversified), and the interior of the continents were relatively dry; northern coniferous forests expanded. Kelp forests appeared in the seas. In North America, the Sierra Nevada Mountains and the Cascade Mountains were formed; in the South America, the Andes Mountains arose. The Bering land bridge formed during the Miocene, connecting Russia and Alaska, allowing many animals to migrat across continents. The Isthmus of Panama also formed during this time. Australia became very dry (but went through wet and dry periods). In Europe, the Mediterranean Sea and Indian Ocean were separated (they had been connected by the Tethys Sea).

MIXOSAURUS(pronounced MIX-oh-SAWR-us) Mixosaurus was an Ichthyosaur 3.25 feet (1 m) long with a dorsal fin and a long toothed snout. It had four short, paddle-shaped flippers, each with five toes; the front flippers were longer than the hind flippers. Mixosaurus lived during the mid-Triassic period in what is now Asia, Europe, North America, and South America. It was not a dinosaur, but another type of extinct reptile. This carnivore ate fish and other sea creatures and gave birth to live young.